3 * File name: ir/ana/irdom.c
4 * Purpose: Construct and access dominator tree.
5 * Author: Goetz Lindenmaier
9 * Copyright: (c) 2002-2003 Universität Karlsruhe
10 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
26 #include "irgraph_t.h" /* To access state field. */
30 #define get_dom_info(bl) (&(bl)->attr.block.dom)
33 /*--------------------------------------------------------------------*/
34 /** Accessing the dominator data structures **/
35 /*--------------------------------------------------------------------*/
37 ir_node *get_Block_idom(const ir_node *bl) {
39 if (get_Block_dom_depth(bl) == -1) {
40 /* This block is not reachable from Start */
43 return get_dom_info(bl)->idom;
46 void set_Block_idom(ir_node *bl, ir_node *n) {
47 dom_info *bli = get_dom_info(bl);
49 assert(get_irn_op(bl) == op_Block);
51 /* Set the immediate dominator of bl to n */
55 * If we don't set the root of the dominator tree
56 * Append bl to the dominates queue of n.
59 dom_info *ni = get_dom_info(n);
61 bli->next = ni->first;
66 int get_Block_pre_num(const ir_node *bl) {
67 assert(get_irn_op(bl) == op_Block);
68 return bl->attr.block.dom.pre_num;
71 void set_Block_pre_num(ir_node *bl, int num) {
72 assert(get_irn_op(bl) == op_Block);
73 bl->attr.block.dom.pre_num = num;
76 int get_Block_dom_depth(const ir_node *bl) {
77 assert(get_irn_op(bl) == op_Block);
78 return bl->attr.block.dom.dom_depth;
81 void set_Block_dom_depth(ir_node *bl, int depth) {
82 assert(get_irn_op(bl) == op_Block);
83 bl->attr.block.dom.dom_depth = depth;
86 unsigned get_Block_dom_tree_pre_num(const ir_node *bl)
89 return get_dom_info(bl)->tree_pre_num;
92 unsigned get_Block_dom_max_subtree_pre_num(const ir_node *bl)
95 return get_dom_info(bl)->max_subtree_pre_num;
98 int block_dominates(const ir_node *a, const ir_node *b)
100 const dom_info *ai, *bi;
102 assert(is_Block(a) && is_Block(b));
103 ai = get_dom_info(a);
104 bi = get_dom_info(b);
105 return bi->tree_pre_num - ai->tree_pre_num
106 <= ai->max_subtree_pre_num - ai->tree_pre_num;
109 ir_node *get_Block_dominated_first(const ir_node *bl)
111 assert(is_Block(bl));
112 return get_dom_info(bl)->first;
115 ir_node *get_Block_dominated_next(const ir_node *bl)
117 assert(is_Block(bl));
118 return get_dom_info(bl)->next;
121 void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
122 irg_walk_func *post, void *env)
129 dominates_for_each(bl, p) {
130 dom_tree_walk(p, pre, post, env);
137 void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
138 irg_walk_func *post, void *env)
140 /* The root of the dominator tree should be the start node. */
141 ir_node *root = get_irg_start_block(irg);
143 assert(irg->dom_state == dom_consistent
144 && "The dominators of the irg must be consistent");
145 assert(root && "The start block of the graph is NULL?");
146 assert(get_dom_info(root)->idom == NULL
147 && "The start node in the graph must be the root of the dominator tree");
148 dom_tree_walk(root, pre, post, env);
151 static void assign_tree_pre_order(ir_node *bl, void *data)
153 unsigned *num = data;
154 dom_info *bi = get_dom_info(bl);
156 bi->tree_pre_num = (*num)++;
159 static void assign_tree_pre_order_max(ir_node *bl, void *data)
161 dom_info *bi = get_dom_info(bl);
164 unsigned children = 0;
166 for(p = bi->first; p; p = get_dom_info(p)->next) {
167 unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
168 max = max > max_p ? max : max_p;
172 bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
173 assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
176 /*--------------------------------------------------------------------*/
177 /* Building and Removing the dominator datastructure */
178 /*--------------------------------------------------------------------*/
180 static void count_and_init_blocks(ir_node *bl, void *env) {
181 int *n_blocks = (int *) env;
184 memset(get_dom_info(bl), 0, sizeof(dom_info));
185 set_Block_idom(bl, NULL);
186 set_Block_pre_num(bl, -1);
187 set_Block_dom_depth(bl, -1);
190 /* temporary type used while constructing the dominator tree. */
191 typedef struct tmp_dom_info {
192 ir_node *block; /* backlink */
194 struct tmp_dom_info *semi; /* semidominator */
195 struct tmp_dom_info *parent;
196 struct tmp_dom_info *label; /* used for LINK and EVAL */
197 struct tmp_dom_info *ancestor;/* used for LINK and EVAL */
198 struct tmp_dom_info *dom; /* After step 3, if the semidominator of w is
199 its immediate dominator, then w->dom is the
200 immediate dominator of w. Otherwise w->dom
201 is a vertex v whose number is smaller than
202 w and whose immediate dominator is also w's
203 immediate dominator. After step 4, w->dom
204 is the immediate dominator of w. */
205 struct tmp_dom_info *bucket; /* set of vertices with same semidominator */
208 /* Struct to pass info through walker. */
216 /* Walks Blocks along the out datastructure. If recursion started with
217 Start block misses control dead blocks. */
218 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
219 tmp_dom_info *tdi_list, int* used) {
223 assert(get_irn_op(bl) == op_Block);
224 if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
226 mark_Block_block_visited(bl);
227 set_Block_pre_num(bl, *used);
229 tdi = &tdi_list[*used];
234 tdi->ancestor = NULL;
236 tdi->parent = parent;
240 for(i = 0; i < get_Block_n_cfg_outs(bl); i++) {
241 ir_node *pred = get_Block_cfg_out(bl, i);
242 assert(get_irn_opcode(pred) == iro_Block);
243 init_tmp_dom_info(pred, tdi, tdi_list, used);
248 dom_compress (tmp_dom_info *v)
250 assert (v->ancestor);
251 if (v->ancestor->ancestor) {
252 dom_compress (v->ancestor);
253 if (v->ancestor->label->semi < v->label->semi) {
254 v->label = v->ancestor->label;
256 v->ancestor = v->ancestor->ancestor;
260 /* if V is a root, return v, else return the vertex u, not being the
261 root, with minimum u->semi on the path from v to its root. */
262 INLINE static tmp_dom_info*
263 dom_eval (tmp_dom_info *v)
265 if (!v->ancestor) return v;
270 /* make V W's ancestor */
272 dom_link (tmp_dom_info *v, tmp_dom_info *w)
277 /* Computes the dominator trees. Sets a flag in irg to "dom_consistent".
278 If the control flow of the graph is changed this flag must be set to
279 "dom_inconsistent". */
280 void compute_doms(ir_graph *irg) {
281 ir_graph *rem = current_ir_graph;
282 int n_blocks, used, i, j;
283 tmp_dom_info *tdi_list; /* Ein Golf? */
285 current_ir_graph = irg;
287 /* Update graph state */
288 assert(get_irg_phase_state(current_ir_graph) != phase_building);
289 current_ir_graph->dom_state = dom_consistent;
291 /* Count the number of blocks in the graph. */
293 irg_block_walk(get_irg_end(current_ir_graph), count_and_init_blocks, NULL, &n_blocks);
295 /* Memory for temporary information. */
296 tdi_list = xcalloc(n_blocks, sizeof(tdi_list[0]));
298 /* We need the out datastructure. */
299 if (current_ir_graph->outs_state != outs_consistent)
300 compute_outs(current_ir_graph);
302 /* this with a standard walker as passing the parent to the sons isn't
305 inc_irg_block_visited(current_ir_graph);
306 init_tmp_dom_info(get_irg_start_block(current_ir_graph), NULL, tdi_list, &used);
307 /* If not all blocks are reachable from Start by out edges this assertion
309 assert(used == n_blocks && "Precondition for dom construction violated"); */
313 for (i = n_blocks-1; i > 0; i--) { /* Don't iterate the root, it's done. */
315 tmp_dom_info *w = &tdi_list[i];
319 irn_arity = get_irn_arity(w->block);
320 for (j = 0; j < irn_arity; j++) {
321 ir_node *cf_op = get_Block_cfgpred(w->block, j);
322 ir_node *pred = get_nodes_block(cf_op);
325 if ((is_Bad(cf_op)) || (is_Bad(pred)) ||
326 (get_Block_pre_num (pred) == -1))
327 continue; /* control-dead */
329 u = dom_eval (&tdi_list[get_Block_pre_num(pred)]);
330 if (u->semi < w->semi) w->semi = u->semi;
332 /* Add w to w->semi's bucket. w is in exactly one bucket, so
333 buckets can ben implemented as linked lists. */
334 w->bucket = w->semi->bucket;
337 dom_link (w->parent, w);
340 while (w->parent->bucket) {
342 v = w->parent->bucket;
343 /* remove v from w->parent->bucket */
344 w->parent->bucket = v->bucket;
348 if (u->semi < v->semi)
355 tdi_list[0].dom = NULL;
356 set_Block_idom(tdi_list[0].block, NULL);
357 set_Block_dom_depth(tdi_list[0].block, 1);
358 for (i = 1; i < n_blocks; i++) {
359 tmp_dom_info *w = &tdi_list[i];
361 if (w->dom != w->semi) w->dom = w->dom->dom;
362 set_Block_idom(w->block, w->dom->block);
363 set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
367 /* free(tdi_list); @@@ does not work !!?? */
368 current_ir_graph = rem;
370 /* Do a walk over the tree and assign the tree pre orders. */
372 unsigned tree_pre_order = 0;
373 dom_tree_walk_irg(irg, assign_tree_pre_order,
374 assign_tree_pre_order_max, &tree_pre_order);
378 void free_dom_and_peace(ir_graph *irg) {
379 /* Update graph state */
380 assert(get_irg_phase_state(current_ir_graph) != phase_building);
381 current_ir_graph->dom_state = dom_none;
383 /* With the implementation right now there is nothing to free,
384 but better call it anyways... */